This year, Google and IBM have reached milestones in quantum computing. Google built a computer that solved a math problem 1,000 times faster than other supercomputers while IBM made a computer that reversed time. These feats hint at bending the rules of time.
Quantum computing is a dizzying concept of wavelengths, chemistry, and chaos. However, popular website Vox, who broke the story about Google’s quick-thinking quantum computer, described it a bit more simply. Traditional computers use the flow of electricity as a basis for operation, rendering all functions into turning on or off like a light switch—the “zeroes and ones” of binary code. Quantum computers, however, are based on physical properties of subatomic particles like electrons, “sorting through all the possible paths it can take before finding the right ones,” according to the website. In the spring, Astronomy.com reported, an IBM quantum computer ran a program of jumbled zeroes and ones to run backwards through time and find their original stable states of code. Astronomy likened it to dropping a handful of glass shards and seeing them come together as an unbroken mirror. This very abstract experiment raises questions about time travel, thermodynamics, and Einstein.
“In 1940, [Austrian mathematician Kurt] Gödel fled Nazi Germany and immigrated to the United States, much as Einstein himself had done seven years earlier,” said Dr. Dan Hooper, Senior Scientist and Head of the Theoretical Astrophysics Group at the Fermi National Accelerator Laboratory. “And like Einstein, Gödel took a position at the Institute for Advanced Study at Princeton, where he became one of Einstein’s closest friends.”
According to Dr. Hooper, Gödel became convinced that our thoughts on the passing of time had serious logical inconsistencies. He said that we tend to think of things happening in either the past, present, or future tenses, but Einstein’s theory of relativity changed that. Then, Alexander Friedmann theorized that the universe is expanding or contracting with time—a model still in use today. Gödel, however, had another theory.
“Like these others, Gödel’s solution included a homogeneous distribution of matter as well as a cosmological constant,” Dr. Hooper said. “But in addition to these more common features, the matter in the universe described by Gödel’s solution was also rotating about an axis.”
In other words, the entire universe was an enormous merry-go-round, which is the most important feature of Gödel’s universe theory. “And it’s this feature that makes time behave differently than it does in most other cosmological solutions,” Dr. Hooper said. “In other words, it allows for time travel.”
According to Gödel’s universe, Dr. Hooper said, time functions more like “an additional dimension of space” than the constant and steady march from one second to the next. Put simply, just as you can walk forwards or backwards in any open space like your living room or a field, you should be able to walk forwards or backwards in time.
“The Grandfather Paradox“
The most famous problem with theoretical time travel is known as “The Grandfather Paradox,” and Dr. Hooper described it as plainly as it gets. To start, imagine that he travels back in time to when his grandfather was still young.
“At this point, I encounter and kill my own grandfather while he’s still a child,” he said. “As a consequence of these actions, my grandfather never grows up, he never meets my grandmother, and he never has any children or grandchildren. This means I’m never born.”
“Therefore, I never exist, and that means that I never travel backwards through time to kill my grandfather. So, since he was never killed, my grandfather survives to meet my grandmother, and they do have children and grandchildren together. And so once again, I do exist, and then I do travel through time to kill my grandfather.”
That’s the paradox. The Grandfather Paradox renders a “self-consistent timeline” impossible, to borrow Dr. Hooper’s phrasing.
Humanity is still a long way from looking into The Grandfather Paradox and Gödel’s model of the universe practically. However, with Google and IBM developing quantum computers that can play with the theories of relativity and time travel, we may one day answer that question—or maybe we already have, but traveled back to erase the evidence.
Dr. Dan Hooper contributed to this article. Dr. Hooper is a senior scientist and the head of the Theoretical Astrophysics Group at the Fermi National Accelerator Laboratory (Fermilab). He is also Associate Professor of Astronomy and Astrophysics at the University of Chicago. Dr. Hooper received his Ph.D. in Physics from the University of Wisconsin–Madison.